[The pathogens of Taiwan mosquitoes--Coelomomyces species]

A brief mention was made of the history of world studies on the Coelomomyces fungi, the life cycle of the fungi, their importance as biological agents for mosquito control, and the known ecological information concerning the Taiwan mosquitoes parasitized by the fungi. Special accounts were made of the results of experiments infecting four mosquito species, Aedes aegypti, Ae. albopictus, Ae. triseriatus and Tripteroides aranoides with Coelomomyces stegomyiae var. chapmani, using the copepod, Phyllognathopus viguieri as an alternate host. The dead 4th instar larvae of Ae. albopictus containing sporangia were put together with healthy copepods for 10 days, then healthy 2nd instar mosquito larvae were added for a 1-day exposure. Then the larvae were transferred to clean water and subsequent examinations for signs of infection were made at 3-day intervals for a period of 21 days. The experiments demonstrated an infection rate of 59.7% and 90% respectively for Ae. albopictus and Ae. aegypti in the first trial, 18.5% and 23.3% in the 2nd trial, and none in the 3rd trial. The low infection rate in the 2nd trial and no infection in the 3rd trial were thought to be due to the extensive contamination of test water with algae. Therefore, in the 4th trial the rearing water was renewed with dechlorinated tap water and new copepods instroduced. The infection rate again rose to 41.1% and 56% respectively for the two species. Experiments with Ae. triseriatus and Tp. aranoides failed to produce signs of infection. Experimental infection of susceptible Ae. albopictus larvae with the sporangia stored at 8 degrees C showed that storage for one month produced an infection rate of 38.2%. However, storage for two months or longer produced no infection in the larvae of the same mosquito species.